The principle parts of a heald frame are composed of frame staves which provide its upper and lower frame members and side stays which provide its right and left frame members. A heald frame has two carrier rods, upper and lower, placed along the frame staves, to which multiple healds are attached to support warps. The heald frame is incorporated in a loom to move reciprocally in the vertical direction.
In recent looms, due to the increased operating speed, heald frames move reciprocally in the vertical direction at a very high speed, which causes deformations due to such repetitive movement. In a heald frame, the severest deformation occurs in the frame staves, which are arcuately bent by the repeated flexing during up and down movement. The deformation of frame staves further increases when a loom is operated at a higher speed and/or longer frame staves are used. Such increased deformation causes breakage of healds or cutting of warps.
Conventionally, in order to suppress such deformation, thicker frame staves or laying down center stays at appropriate locations between the upper and lower frame staves have been tried. However, the use of thicker frame staves is not preferable, because it leads to a weight increase, which is not desired for a high-speed loom. The provision of center stays also has disadvantages because the center stays must be positioned in a manner that cuts between the aligned healds. Since thicker and stronger stays cannot be used, the center stays may be accidentally broken when a strong deformative force occurs in the heald frame. In addition, as they must be installed with the heald frame incorporated in a loom and warps in place, the installation is difficult, and users generally hesitate to use them.